1. Field of the Invention
This invention relates to a multi-beam semiconductor laser having plural emission regions which are formed on the same substrate, and which can be driven independently, and a method for producing the multi-beam semiconductor laser. More specifically, the multi-beam semiconductor laser has so designed that the plural emission regions are formed in the same active layer on the same substrate.
2. Related Background Art
Presently, a semiconductor laser has been widely used for a laser printer, an optical disk, etc., however, the drawing (printing) speed of the laser printer or the data transfer speed of the optical disk has been not necessarily sufficiently high. If two laser beams which can be generated independently and adjacently to each other on a single substrate, a system having the drawing (printing) speed and data transfer speed which are two times as high as those of an ordinary system could be expected to be implemented with one optical system. In order to implement such a system, a multi-beam semiconductor laser has been researched and developed.
It has been conventionally believed that each of plural emission regions can not be independently driven due to electrical cross-talk when active layers for the emission regions are not physically separated from one another. This is pointed out in "Properties of closely spaced independently addressable lasers fabricated by impurity-induced disordering", Appl. Phys, Lett. 56, (17), Apr. 23, 1990.
Therefore, no multi-beam semiconductor laser in which the active layers are not separated, that is, the emission regions are formed in the same active layer has conventionally existed in the multi-beam semiconductor lasers in which the emission regions are independently driven.
One of the conventional multi-beam semiconductor lasers in which the emission regions are independently driven is disclosed in Japanese Laid-open Patent Application No. 3-145779.
In addition, there has been known a multi-bean semiconductor laser in which the respective emission regions are not driven independently, but simultaneously to merely obtain high output power. This type of multi-beam semiconductor laser is disclosed in "High-power AlGaInP three-ridge type LASER diode array", ELECTRONICS LETTERS 17th 1988 Vol. 24 No. 6.
A technique using an etching stopper is disclosed in "HIGH-POWER OPERATING OF A TRANSVERSE-MODE STABILIZED AlGaInP VISIBLE LIGHT (.lambda..sub.L)=683 nm) SEMICONDUCTOR LASER", ELECTRONICS LETTERS Aug. 27, 1987, Vol. 23, No. 18, p938-939, for example.